Spring Seminar Series: Sarah Tolbert
Sarah Tolbert (UCLA)
THIS EVENT HAS CHANGED TO A DIGITAL FORMAT.
ABSTRACT: In the first part of this talk, we will consider ways to increase electrical conductivity in plastic conductors based on semiconducting polymers. Chemically doping these polymers using strong oxidizing or reducing agents can dramatically improve charge carrier density, but overall conductivity is still limited by Coulomb attraction between dopants and charge balancing counter-ions. In this presentation, we explore the use of large dodecaborane clusters as both oxidizing agents and delocalized counter-ions that limit Coulomb attraction. Using the chemical tunability of these clusters, we are further able to isolate and explore many of the parameters that control carrier mobility in plastic conductors. The second part of the talk moves from organic to inorganic materials, focusing on a family of fast-charging energy storage materials call pseudocapacitors and on the development of architectures to enhance charging speed. We find that in optimized nanoporous materials, the nanoscale structure and porosity can produce a very desirable combination of electrical connectivity, electrolyte access to the interior of the material, and very short solid-state diffusion lengths for lithium ions, all of which facilitate fast charge and discharge. In addition, using operando diffraction collected during electrochemical cycling, we find that many nanoscale materials show suppression of the intercalation induced phase transition that can cause kinetic limitations in bulk materials.